Maleated high acid number high molecular weight polypropylene of low color

ABSTRACT

A process for the manufacture of maleated polypropylenes having an acid number greater than 4.5, a yellowness index color of no greater than 76, and a number average molecular weight of at least 20,000. The process for making the maleated polypropylenes includes forming a mixture of molten polypropylene and molten maleic anhydride in a reactor, introducing a free radical initiator into the molten mixture to produce a product having maleic anhydride grafted onto the polypropylene, and recovering a high acid number, high molecular weight maleated polypropylene of low color from the reactor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of the earlier filedapplication having U.S. Ser. No. 09/951,985 filed Sep. 11, 2001 nowabandoned; which was a continuation of the application having U.S. Ser.No. 09/498,574 filed Feb. 4, 2000 now abandoned; which was acontinuation of the application having U.S. Ser. No. 09/256,830 filedFeb. 24, 1999, now U.S. Pat. No. 6,046,279; which was a divisional ofthe application having U.S. Ser. No. 08/859,628 filed May 20, 1997, nowU.S. Pat. No. 5,955,547; which was a continuation of the applicationhaving U.S. Ser. No. 08/802,595 filed Feb. 19, 1997, now abandoned;which was a continuation of the application having U.S. Ser. No.08/296,208 filed Aug. 25, 1994, now abandoned; wherein this applicationclaims benefit to these earlier filed applications, the entiredisclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel lower color, maleated polypropyleneswith higher acid numbers and higher molecular weights. This inventionalso relates to a novel polypropylene maleation process utilizing lowflow rate polypropylenes involving specified ratios of polypropylene,maleic anhydride, and free radical initiator.

2. Background of the Invention

Grafting of monomers onto polyolefins is well known (see ‘PolymerChemistry’ by M. P. Stevens, (Addison-Wesley), 1975, pp. 196-202).Maleation is a type of grafting wherein maleic anhydride is grafted ontothe backbone chain of a polymer. Maleation of polyolefins falls into atleast three subgroups: maleation of polyethylene, maleation ofpolypropylene, and maleation of copolymers of propylene and ethylene orother monomers.

Maleation of polyethylene provides higher molecular weight products witha noticeable decrease in melt index due to cross-linking, unless specialprovisions are made, (see for example “Journal of Applied PolymerScience”, 44, 1941, N. G. Gaylord et al (1992); and U.S. Pat. Nos.4,026,967; 4,028,436; 4,031,062; 4,071,494; 4,218,263; 4,315,863;4,347,341; 4,358,564; 4,376,855; 4,506,056; 4,632,962; 4,780,228;4,987,190; and 5,021,510). Maleation of polypropylene follows anopposite trend and yields lower molecular weight products with a sharpincrease in flow rate due to fragmentation during the maleation process(see for example U.S. Pat. Nos. 3,414,551; 3,480,580; 3,481,910;3,642,722; 3,862,265; 3,932,368; 4,003,874; 4,548,993; and 4,613,679).Some references in the literature fail to note the difference betweenmaleation of polyethylene and polypropylene, and claim maleation ofpolyolefins with conditions which are useful only for eitherpolyethylene or polypropylene, respectively. In general, conditionswhich maleate polypropylene are not ideal for maleation of polyethylenedue to the opposite nature of the respective maleation chemistries:fragmentation to lower molecular weights for polypropylene andcross-linking to higher molecular weights for polyethylene. This isshown in U.S. Pat. No. 4,404,312. Maleation of copolymers of propyleneand ethylene or other monomers follow the pattern of the majoritycomponent.

Maleations of polypropylene can also be further subdivided into batch orcontinuous processes. In batch processes all of the reactants andproducts are maintained in the reaction for the entire batch preparationtime. In general, batch maleation processes cannot be used competitivelyin commerce due to high cost. Batch processes are inherently moreexpensive due to startup and cleanup costs.

The maleated polypropylenes that are reported in the previous literaturecan also be divided into two product types as a function of whether ornot solvent is involved, either as a solvent during reaction or inworkup of the maleated products. In U.S. Pat. Nos. 3,414,551; 4,506,056;and 5,001,197 the workup of the product involved dissolving the maleatedpolypropylene product in a solvent followed by precipitation, or washingwith a solvent. This treatment removes soluble components and thusvaries both the ‘apparent’ molecular weight and the acid number.Processes using an extruder produce a product in which solvent solublecomponents remain. In addition, extruder processes often incorporate avacuum system during the latter stages of the process to remove volatilelower molecular weight components. Thus different compositions arenecessarily present in products produced in an extruder in contrast tothose products from solvent processes or those which use a solvent inproduct workup.

Another subdivision of maleation of polyolefins concerns the state ofthe reaction process. Solvent processes, or processes where solvent isadded to swell the polypropylene (see U.S. Pat. No. 4,370,450) are oftencarried out at lower temperatures than molten polyolefin (solvent free)processes. Such processes involve surface maleation only, withsubstantial amounts of polypropylene below the surface being maleationfree. Processes using molten polypropylene involve random maleation ofall of the polypropylene. Solvent processes are also more expensive inthat solvent recovery/purification is necessary. Solvent purification iseven more expensive if the process inherently produces volatileby-products, as in maleation. Note that if water is the “solvent”,polypropylene is not soluble and reaction must occur only on the surfaceof the polypropylene solid phase. Further, in aqueous processes maleicanhydride reacts with the water to become maleic acid. In these two waysprocesses containing water are necessarily different from non-aqueousprocesses. In a molten process no solvent or water remains at the end ofthe process to be purified or re-used. Thus a molten process would beenvironmentally “greener” and less expensive.

Present commercial maleation of low flow rate (high molecular weight)polypropylene by continuous processes, such as in an extruder, produceproducts with acid numbers well below 4. These products are used inadhesives, sealants, and coatings and as couplers and compatibilizers inpolymer blends. However, due to the low acid numbers, the adhesion andcoupling properties of these maleated polypropylenes are limited. Asnoted above, attempts to produce higher acid number polypropylene incontinuous processes yield higher colored products with much lowermolecular weight with maleic anhydride conversion efficiencies of 20-30%or lower (see for example U.S. Pat. No. 5,001,197). Attempts to producehigher acid number polyethylene in continuous processes yieldcross-linking, higher color, and gels (see for example U.S. Pat. Nos.4,612,155; 4,639,495; 4,751,270; 4,762,890; 4,857,600; and 4,927,888).The patent literature does describe continuous maleation of high flowrate (low molecular weight) polypropylene waxes to higher acid numbers.However, as noted above the molecular weights of the maleated waxes soproduced are even lower than that of the starting material due tofragmentations during maleation.

In light of the above, it would be very desirable to maleate lower flowrate polypropylenes in a continuous process to higher molecular weightsand higher acid numbers with lower colors than have been known before.It would also be very desirable to maleate these polypropylenes athigher efficiencies.

BRIEF SUMMARY OF THE INVENTION

The composition according to the present invention comprises a maleatedpolypropylene having an acid number greater than 4.5, a yellowness indexcolor of no greater than 76, and a number average molecular weight of atleast 20,000.

The process for the production of high acid number high molecular weightmaleated polypropylene of low color comprises forming a mixture ofmolten polypropylene and molten maleic anhydride, introducing a freeradical initiator into the mixture of molten polypropylene and moltenmaleic anhydride, and recovering high acid number high molecular weightmaleated polypropylene of low color, wherein the weight ratio ofpolypropylene to maleic anhydride is about 10 to 200, the molar ratio ofpolypropylene to free radical initiator is about 200 to 4,000, and themolar ratio of maleic anhydride to peroxide is about 1 to 70, andwherein the melt flow rate of said molten polypropylene is preferablyabout 0.1 to 50 at 230° C.

DETAILED DESCRIPTION

The applicants have unexpectedly discovered a novel continuous processto maleate low flow rate polypropylenes. The compositions so formed arenovel in that the color is lower, the acid number is higher, and themolecular weight is higher than previously known. The process is alsounique in that the efficient use of maleic anhydride is generally muchhigher than expected.

The composition according to the present invention has an acid numbergreater than about 4.5. The maleated polypropylene composition accordingto the present invention preferably has an acid number greater than 5,more preferably between 6 and 70, with an acid number between 9 and 60being most preferred. Generally, at the higher acid numbers theresulting maleated polypropylene exhibits higher adhesiveness to polarsubstrates and thus is more useful in combination with materials used inadhesives and sealants. Additionally, at the higher acid numbers themaleated polypropylene is useful as a compatibilizing agent or couplerwhen used in blends of dissimilar materials, including polymer blendssuch as a nylon and polypropylene blend. At higher acid numbers loweramounts of maleated polypropylene is needed for any of these purposes.However, due to practicality acid numbers generally above 70 aredifficult to produce economically. Thus, practical preferred limits onacid numbers of the maleated polypropylene are below 70.

The composition according to the present invention has a yellownessindex color no greater than 76 or about 75. The yellowness index coloranalysis is illustrated in the examples. At a yellowness index colorless than about 75, the resulting maleated. polypropylene has adesirable color in that when blended with other materials it impartsless of an undesirable yellow tint or brown tint to the final product.Thus, yellowness index colors well below 75 are more preferred. Themaleated polypropylene composition according to the present inventionpreferably has a yellowness index color less than about 65 or 60, morepreferably less than 50 with a yellowness index color less than 40 beingmost preferred.

The composition according to the present invention has a number averagemolecular weight of at least 20,000. This number average molecularweight is preferably as high as possible. At higher number averagemolecular weights the resulting maleated polypropylene is more durableand flexible which is desired in many applications. Thus, the maleatedpolypropylene preferably has a number average molecular weight greaterthan 25,000 and even greater than 30,000. However, the maleatedpolypropylene generally has a number average molecular weight less than100,000 due to fragmentation that occurs during the process of maleatingthe molten polypropylene. Therefore, the maleated polypropylenegenerally has a number average molecular weight for the more preferredcompositions between 25,000 and 80,000 with a number average molecularweight between 30,000 and 70,000 being most preferred.

The composition according to the present invention is made frompolypropylene that contains less than 20 weight percent of a comonomerand is preferably a homopolypropylene containing less than 5 weightpercent of a comonomer, more preferably less than 2 weight percent of acomonomer. At amounts of comonomer higher than 20 weight percent, andsometimes higher than 5 weight percent, the crystallinity of themaleated polypropylene is significantly reduced, and in the case ofethylene as comonomer crosslinking can occur.

The composition according to the present invention can be blended withmany other materials to serve as a compatibilizer, such as in blendswith nylon and polypropylene. This type of blend preferably containsabout 10 to 90 weight percent nylon, about 10 to 90 weight percentpolypropylene, and about 0.1 to 10 weight percent maleatedpolypropylene, more preferably about 25 to 75 weight percent nylon,about 25 to 75 weight percent polypropylene, and about 0.1 to 10 weightpercent maleated polypropylene.

Additionally, the maleated polypropylene composition of the presentinvention can be extended with many components such as wood flour, glassfibers, talc, and mica. The use of these components extend the materialreducing the final cost.

The process according to the present invention for producing the highacid number high molecular weight maleated polypropylene of low colorpreferably includes the use of an extruder as a reactor, the processcomprises

-   -   (a) forming a mixture of molten polypropylene and molten maleic        anhydride at one end of a reactor, wherein the melt flow rate of        said polypropylene is preferably about 0.1 to 50 at 230° C.,    -   (b) mixing a free radical reaction initiator into the mixture of        molten polypropylene and molten maleic anhydride to produce a        maleated polypropylene, and    -   (c) removing the maleated polypropylene product from the        reactor,

wherein the weight ratio of polypropylene to maleic anhydride is about10 to 200, the molar ratio of polypropylene to free radical initiator isabout 200 to 4,000, and the molar ratio of maleic anhydride to freeradical initiator is about 1 to 70. In a preferred embodiment, themaleated polypropylene product, while still in the extruder, issubjected to a vacuum to remove a substantial portion of volatilespresent in the product, and preferably greater than about 80% of thevolatiles are removed. The amount of vacuum that the product is subjectto can be slightly less than atmospheric, i.e., from about 10 to lessthan 100 mm of mercury (Hg) to a vacuum of greater than about 300 mm of(Hg) and preferably greater than about 700 mm of Hg.

The process according to the present invention maleates a moltenpolypropylene that preferably has a melt flow rate of about 0.1 to 50 at230° C. For all practical purposes, a polypropylene with a melt flowrate below 0.1 is difficult to produce and requires significant torquein a twin screw extruder to be able to process. Whereas, a polypropylenewith a melt flow rate greater than 50 to 230° C. yields a maleatedpolypropylene product with a molecular weight that is lower than isgenerally useful according to the present invention. The melt flow rateof the polypropylene used to produce a maleated polypropylene of thepresent invention is more preferably about 0.1 to 40 at 230° C., with amelt flow rate of about 0.1 to 20 at 230° C. being most preferred.

The process according to the present invention uses a free radicalinitiator to initiate the grafting of the maleic anhydride onto themolten polypropylene. Any free radical source could be useful in theprocess of the present invention. However, peroxides are generally morepreferred due to availability and cost. Peroxides with short half livesi.e. less than 3 seconds at 180° C. are less desirable, since asignificantly higher amount of peroxide is needed and results in amaleated polypropylene product of poor color and higher cost. Thepreferred peroxides are alkyl peroxides, more preferable dialkylperoxides. Examples of suitable peroxides useful in the process of thepresent invention include ditertiary butyl peroxide, tertiary butylhydroperoxide, cumene hydroperoxide, p-menthane peroxide, p-menthanehydroperoxide and 2,5-dimenthyl-2,5-bis-(t-butylperoxy)hexane withditertiary butyl peroxide and 2,5-bis-(t-butylperoxy)hexane being mostpreferred.

The process according to the present invention is conducted in acontinuous process. Any continuous process can be used in the practiceof the present invention. However, stirred pot reactors with powerfulstirring mechanisms or screw extruders are favored, with screw extrudersgenerally being more preferred due to the ease in operation andacceptability in manufacturing processes. Twin-screw extruders are themost preferred screw extruders due to their ease of use and efficientmixing action. Screw extruders are also more preferred in that thepolypropylene is maleated continuously with a shorter residence time inthe reaction zones. The use of a screw extruder in the process of thepresent invention aids in the production of maleated polypropylenes ofimproved color and higher molecular weight due in part to lessfragmentation of the polypropylene.

The process according to the present invention is preferably conductedat a weight ratio of polypropylene to maleic anhydride between 10 and200, more preferably between 15 and 120, even more preferably between 20and 100, with a weight ratio of polypropylene to maleic anhydride ofabout 20 to 60 being most preferred. At amounts of polypropylene/maleicanhydride below the ratio of 10 too much maleic anhydride is present andthe efficiencies are dramatically reduced. Whereas, at ratios above 200the amount of maleation in the final maleated polypropylene issignificantly lower. Such ratios simply increases the need for longerresidence time or recycle of low acid number maleated polypropylene.

The residence time of the polypropylene in the continuous reactordepends upon the pumping rate of the polypropylene and the size (volume)of the reactor. This time is generally longer than three times the halflife of the free radical initiator so that a second pass through thereactor is not needed to obtain sufficient maleation of thepolypropylene. In a stirred reactor the residence time generally variesfrom about 5 minutes to 1 hour, more preferably about 10 minutes to 30minutes. In a screw extruder this time generally varies from about 1 to3 minutes at RPMs of 50 to 400 for a single screw and about 0.45 to 2.5minutes with twin screws, more preferably about 1 to 2 minutes at RPMsof 150 to 300 with twin screws. As shown in the examples, at certain setamounts of reactants (within the general ratios of reactants required inthe present invention) a polypropylene of lower than desired acid numberis produced. In this instance the RPM in a screw extruder can be reducedor the residence time increased such that the acid number is increasedto be within the more desired acid number limits. Although not shown, athree dimensional plot of maleic anhydride, peroxide and extruder RPMgenerates a well defined volume from which one skilled in the art wouldbe able to optimize a maleated polypropylene in accordance with thepresent invention.

The molar ratio of polypropylene to free radical initiator used in themaleation process according to the present invention is preferably about200 to 4,000, more preferably about 210 to 3,500, with a molar ratio ofpolypropylene to free radical initiator of about 270 to 2,100 being mostpreferred. At amounts below the molar ratio of 200 the presence of highamounts of free radical initiator produces excess fragmentation of thepolypropylene resulting in a lower molecular weight polypropylene. Atamounts above the molar ratio of 4,000 the free radical initiator is atsuch a low concentration that efficient maleation is not obtainable.

The process according to the present invention is preferably conductedat a molar ratio of maleic anhydride to free radical initiator betweenabout 1 and 70, more preferably between about 2 and 60, even morepreferably between about 3 and 50, with a molar ratio of maleicanhydride to free radical initiator of about 3.5 to 15 being mostpreferred. At molar ratios below 1 the amount of free radical initiatoris significantly higher than required for the particular amount ofmaleation on the polypropylene, and thus increases fragmentation whilenot significantly increasing the acid number of the maleatedpolypropylene. For amounts such that the molar ratio of maleic anhydrideto free radical initiator is above 70, the efficiencies of the graftingof maleic anhydride onto the polypropylene is dramatically reduced andthe color of the resulting product is inferior.

The maleic anhydride useful for the present process is any commercialgrade of maleic anhydride. Those with maleic anhydride contents of95-100% are preferred in that fewer volatile by-products must be handledby the vacuum system. Molten maleic anhydride with a purity over 99% ismost preferred for the same reason, fewer volatiles are produced to behandled by the vacuum system.

The process according to the present invention is generally conducted ata temperature above the melting point of the polypropylene. Thistemperature is preferably between 160 and 220° C., more preferablybetween 180 and 210° C., with a temperature between 190 and 205° C.being most preferred. At temperatures much below 160 the viscosity ofthe molten polypropylene is too high to be efficiently pumped throughthe screw extruder. At temperatures much above 220° C. the fragmentationof the molten polypropylene dramatically increases and molecular weightdecreases.

The process according to the present invention is generally conductedsuch that a vacuum is used at or after step (c) to remove volatiles fromthe maleated polypropylene product.

The process according to the present invention is generally efficient,grafting onto polypropylene a high percent of the maleic anhydridepresent during the reaction, thus producing a maleated polypropylenewith grafted maleic anhydride at a preferred efficiency percent above35. This percent maleic anhydride incorporated into polypropylene can beup to or near 100 percent. However, this efficiency rate is generallyover about 40 and up to 93 percent, more preferably at least 49 percent.At efficiency rates below 35 percent, maleic anhydride recovery isincreased and cost per unit maleation onto the polypropylene is alsoincreased. However, efficiencies at or below 85 percent are generallyacceptable.

The following examples are intended to illustrate the present inventionbut should not be interpreted as a limitation upon the reasonable scopethereof.

EXAMPLES

Values of the acid number as shown in Table 1 are the average of atleast 4 determinations taken on samples obtained at 15 minute intervalsduring an hour of production. An acid number is defined as the number ofmilligram of KOH which are required to neutralize one gram of sample.Acid numbers were obtained by titrating weighed samples dissolved inrefluxing xylene with methanolic potassium hydroxide usingphenolphthalein as an indicator. End points were taken when the pinkcolor of the indicator remained 10 seconds.

Color was measured as ‘yellowness index’ according to ASTM RecommendedPractice E 308 for Spectrophotometry and Description of color in CIE1931 System.

Efficiencies, noted in Table 1 as ‘% maleic anhydride (MA) used’, werecalculated based on the percent of the fed MA which was incorporatedinto the product. (Efficiency of ‘% MS used’ is defined as the pounds ofMA grafted into the polymer divided by the pounds of MA pumped into theextruder multiplied by 100.)

The amount of unreacted maleic anhydride remaining in the samples wasfound to be negligible by using a method based on extraction andhydrolysis. A 1 gram sample was heated with 10 ml of methylene chlorideand 10 ml. of water at 125° C. in a pressure vessel for 1 hour andcooled to room temperature. One ml of the clear, top aqueous layer wasthen diluted to 10 ml with water and analyzed for U.V. absorption at 208nm. A calibrated graph of absorbance vs. percent MA from known samplesfacilitated determination of ‘% free MA’, or the amount of unreacted MAexpressed as weight percent. Values ranged from 0.1 to 0.4 wt-%.

Molecular weights were obtained by using a Waters 150° C. Gel PermeationChromatograph with three Waters HT columns (10,000; 100,000; and1,000,000 angstroms) at 140° C. The calibration standard waspolypropylene (Mw=108,000; Mn=32,500). Samples were dissolved ino-di-chlorobenzene at 140° C.

In order to calculate the moles of polypropylene for the ratio ofpolypropylene/peroxide (moles/moles) the weight of polypropylene wasdivided by 42, the molecular weight of propylene.

Example 1

Pellets of polypropylene from Eastman Chemical Company as TENITE P4-026with a melt flow rate of 1.2 were fed into the inlet hopper of a 90 mmtwin screw extruder having 13 consecutive equivalent barrels all at 200°C. at 150 rpm at a rate of 272 kg per hour. Molten maleic anhydride at90° C. was pumped into port 1 on barrel 1 adjacent to the inlet hopperat a rate of 10.9 kg per hour. LUPERSOL 101[2,5-dimethyl-2,5-bis-(t-butylperoxy)hexane] from Elf Atochem at 1.1 kgper hour was pumped into port 2 on barrel 2. A vacuum, 30 inches ofMercury, (760 mm) was pulled on port 8 and 10 located on barrels 8 and10. The pale yellow product was extruded as molten strands from barrel13, was solidified under water, and was then cut into pellets. Theproduct was analyzed with the following results: acid number=8.7; numberaverage molecular weight (Mn)=48,000; weight average molecular weight(Mw)=119,000; yellowness index color=51; and percent maleic anhydrideutilized=37% (37% efficiency).

Example 2

This example was carried out essentially as in Example 1 except that theRPM was changed to 292. The maleated polypropylene produced was analyzedwith the following results: acid number=10.1; Mn=43,000; Mw=105,000;yellowness index color=49; and maleic anhydride used=43% (43%efficiency).

Example 3

This example was carried out essentially as in Example 2 except that theamount of LUPERSOL 101 was changed to 2.4 kg per hour. The maleatedpolypropylene, produced was analyzed with the following results: acidnumber=16.4; Mn=30,000; Mw=72,000; yellowness index color-48; and maleicanhydride used=70% (70% efficiency).

Example 4

This example was carried out essentially as in Example 3 except that theRPM was changed to 150. The maleated polypropylene produced was analyzedwith the following results: acid number=14.6; Mn=31,000; Mw=87,000;yellowness index color=56; and maleic anhydride used 62% (62%efficiency).

Example 5

This example was carried out essentially as in Example 4 except that theLUPERSOL 101 was changed to 0.5 kg per hour and the maleic anhydride waschanged to 4.5 kg per hour. The maleated polypropylene produced wasanalyzed with the following results: acid number=5.9; Mn=47,000;Mw=118,000; yellowness index color=25; and maleic anhydride used=60%(60% efficiency).

Example 6

This example was carried out essentially as in Example 5 except that theLUPERSOL 101 was changed to 1.1 kg per hour. The maleated polypropyleneproduced was analyzed with the following results: acid number=9.1;Mn=36,000; Mw=89,000; yellowness index color=24; and maleic anhydrideused=93% (93% efficiency).

Example 7

This example was carried out essentially as in Example 6 except that theRPM was changed to 292. The maleated polypropylene produced was analyzedwith the following results: acid number=4.8; Mn=51,000; Mw=130,000;yellowness index color=33; and maleic anhydride used=49% (49%efficiency).

Example 8

This example was carried out essentially as in Example 7 except that theLUPERSOL 101 was changed to 0.5 kg per hour. The maleated polypropyleneproduced was analyzed with the following results: acid number=3.0;Mn=57,000; Mw=148,000; yellowness index color=32; and maleic anhydrideused=31% (31% efficiency).

Example 9

This example was carried out essentially as in Example 8 except that theLUPERSOL 101 was changed to 0.3 kg per hour. The maleated polypropyleneproduced was analyzed with the following results: acid number=1.8;Mn=65,000; Mw=165,000; yellowness index color=33; and maleic anhydrideused 18% (18% efficiency).

Example 10

This example was carried out essentially as in Example 9 except that,the RPM was changed to 150. The maleated polypropylene produced wasanalyzed with the following results: acid number=3.5; Mn=58,000;Mw=145,000; yellowness index color=23; and maleic anhydride used=36%(36% efficiency).

Example 11

This example was carried out essentially as in Example 10 except thatthe maleic anhydride was changed to 10.9 kg per hour. The maleatedpolypropylene produced was analyzed with the following results: acidnumber=5.5; Mn=64,000; Mw=168,000; yellowness index color=36; and maleicanhydride used=23% (23% efficiency).

Example 12

This example was carried out essentially as in Example 11 except thatthe RPM was changed to 292. The maleated polypropylene produced wasanalyzed with the following results: acid number=3.6; Mn=60,000;Mw=150,000; yellowness index color=47; and maleic anhydride used=15%(15% efficiency).

Example 13

This example was carried out essentially as in Example 12 except thatthe LUPERSOL 101 was changed to 0.5 kg per hour. The maleatedpolypropylene produced was analyzed with the following results: acidnumber=6.0; Mn=63,000; Mw=135,000; yellowness index color=44; and maleicanhydride used=26% (26% efficiency).

Example 14

This example was carried out essentially as in Example 1 except that theRPM was changed to 200 and the maleic anhydride was changed to 16.3. Themaleated polypropylene produced was analyzed with the following results:acid number=5.4; Mn=60,000; Mw=143,000; yellowness index color=64; andmaleic anhydride used 15% (15% efficiency).

Example 15

This example was carried out essentially as in Example 14 except thatthe RPM was changed to 292. The maleated polypropylene produced wasanalyzed with the following results: acid number=4.2; Mn=71,000;Mw=190,000; yellowness index color=63; and maleic anhydride used=12%(12% efficiency).

Example 16

This example was carried out essentially as in Example 15 except thatthe maleic anhydride was 21.8 kg per hour. The maleated polypropyleneproduced was analyzed with the following results: acid number=3.7;Mn=68,000; Mw=192,000; yellowness index color=76; and maleic anhydrideused=8% (8% efficiency).

Example 17

This example was carried out essentially as in Example 16 except thatthe LUPERSOL 101 was changed to 4.5 kg per hour. The maleatedpolypropylene produced was analyzed with the following results acidnumber=9.0; Mn=67,000; Mw=177,000; yellowness index color=75; and maleicanhydride used=19% (19% efficiency).

Example 18

This example was carried out essentially as in Example 17 except thatthe maleic anhydride was 16.3 kg per hour. The maleated polypropyleneproduced was analyzed, with the following results: acid number=12.0;Mn=54,000; Mw=129,000; yellowness index color=70; and maleic anhydrideused=34%. (34% efficiency).

Example 19

This example was carried out essentially as in Example 2 except that theLUPERSOL 101 was changed to 3.4 kg per hour. The maleated polypropyleneproduced was analyzed with the following results: acid number=16.9;Mn=34,000; Mw=82,000; yellowness index color=50; and maleic anhydrideused=72% (72% efficiency).

Example 20

This example was carried out essentially as in Example 15 except thatthe LUPERSOL 101 was changed to 0.5 kg per hour. The maleatedpolypropylene produced was analyzed with the following results: acidnumber=4.0; Mn=62,000; Mw=159,000; yellowness index color=58; and maleicanhydride used=11% (11% efficiency).

Example 21

This example was carried out essentially as in Example 9 except that themaleic anhydride was changed to 2.3 kg per hour. The, maleatedpolypropylene produced was analyzed with the following results: acidnumber=2.4; Mn=65,000; Mw=152,000; yellowness index color=20; and maleicanhydride used=49% (49% efficiency).

Example 22

This example was carried out essentially as in Example 21 except thatthe RPM was changed to 150. The maleated polypropylene produced wasanalyzed with the following results: acid number=4.4; Mn=53,000;Mw=124,000; yellowness index color=23; and maleic anhydride used=90%(90% efficiency).

The above examples are summarized below in Table 1 below along with thethree important ratios.

TABLE I Reagents Product Properties Reagent Ratios Perox MA kg MA % MAAcid Mn, Mw, Index PP/MA PP/Perox MA/perox # RPM kg/hr kg/hr Used Used #k k Color kg/kg mole/mole mole/mole 1 150 1.1 10.9 4.0 37 8.7 48 119 5125 1710.0 29.4 2 292 1.1 10.9 4.7 43 10.1 43 105 49 25 1710.0 29.4 3 2922.4 10.9 7.6 70 16.4 30 72 48 25 783.8 13.5 4 150 2.4 10.9 6.7 62 14.631 87 56 25 783.8 13.5 5 150 0.5 4.5 2.7 60 5.9 47 118 25 60 3762.0 26.76 150 1.1 4.5 4.2 93 9.1 36 89 24 60 1710.0 12.1 7 292 1.1 4.5 2.2 494.8 51 130 33 60 1710.0 12.1 8 292 0.5 4.5 1.4 31 3.0 57 148 32 603762.0 26.7 9 292 0.3 4.5 0.8 18 1.8 65 165 33 60 6270.0 44.4 10 150 0.34.5 1.6 36 3.5 58 145 23 60 6270.0 44.4 11 150 0.3 10.9 2.5 23 5.5 64168 36 25 6270.0 107.6 12 292 0.3 10.9 1.7 15 3.6 60 150 47 25 6270.0107.6 13 292 0.5 10.9 2.8 26 6.0 63 135 44 25 3762.0 64.6 14 200 1.116.3 2.5 15 5.4 60 143 64 17 1710.0 43.9 15 292 1.1 16.3 2.0 12 4.2 71190 63 17 1710.0 43.9 16 292 1.1 21.8 1.7 8 3.7 68 192 76 13 1710.0 58.717 292 4.5 21.8 4.2 19 9.0 67 177 75 13 418.0 14.3 18 292 4.5 16.3 5.534 12.0 54 129 70 17 418.0 10.7 19 292 3.4 10.9 7.8 72 16.9 34 82 50 25553.2 9.5 20 292 0.5 16.3 1.9 11 4.0 62 159 58 17 3762.0 96.6 21 292 0.32.3 1.1 49 2.4 65 152 20 120 6270.0 22.7 22 150 0.3 2.3 2.0 90 4.4 53124 23 120 6270.0 22.7

In Examples 23 and 24 the following test procedures were used inevaluating the analytical properties of the polypropylene functionalizedin accordance with the present invention.

-   -   1. Acid Number—acid number was determined in accordance with        ASTM D1386-83 with the following modifications: a 0.05 N sodium        hydroxide (NaOH) in methanol solution was substituted for the        0.1 N aqueous solution of potassium hydroxide in ethanol and the        sample size was increased from 1-2 grams to 5 grams, and the        weighing accuracy was changed from 0.001 to 0.0001 grams.    -   2. Color—pellet color was measured as “yellowness index” in        accordance with ASTM D1925 using a standard Gardner BYK        Color-View™ laboratory instrument.    -   3. Viscosity, expressed in centipoise (cP), was determined in        accordance with ASTM D-3236 utilizing a Brookfield Model        RVDV-II+digital Viscometer with a SC 4-27 spindle and a        Brookfield Model 74R Temperature Controller set to 190° C., with        the following exceptions:    -   a. viscosity was recorded 20 minutes after beginning spindle        rotation in the sample;    -   b. only single measurements were taken for each sample; and    -   c. the rotational speed was 3 rpm.    -   4. The molecular weights were measured using a Polymer Labs gel        permeation chromatography GPC 210 Plus with three each 10 micron        mixed B columns. The polymer was dissolved in trichlorobenzene        using a 1 ml/min flowrate at a temperature of 135° C. The        instrument was calibrated using an American Polymer Standards        Corporation PP-105K polypropylene with a broad standard.

The feed materials used in Examples 23 and 24 were:

-   -   1. A nominal 1 Melt Flow Rate (MFR) polypropylene homopolymer        available from Huntsman under the trade name Huntsman        P4-G2Z-026.    -   2. Maleic anhydride briquettes available from Huntsman were        melted at 130° F. and fed as a molten stream into the extruder        as described below.    -   3. Lupersol 101 peroxide,        (2,5-dimethyl-2,5-bis-(t-butylperoxy)hexane), was used as an        initiator.

Broadly, the following procedure was used to produce the functionalizedpolypropylenes: solid pellets of the nominal 1 melt flow rate Huntsmanhomopolymer polypropylene were fed at a rate of 1316 pounds/hour into aCentury™ brand 92mm×11 barrels long twin-screw co-rotating extruder andmelted. Molten maleic anhydride at 25 pounds per hour and a temperatureof 130° F. was introduced into the extruder and mixed with the meltedpolypropylene to form a melt blend. The free radical initiator, Lupersol101, was introduced and mixed with the melt blend at a rate of 4.68pounds/hour. The resultant mixture was mixed in the extruder for a timesufficient to form the desired functionalized polypropylene. Desirably,the functionalized polypropylene is subjected to a vacuum vented portduring extrusion to remove volatile materials from the melt mixture. Thefunctionalized polypropylene was then forced through a die, cooled usinga standard cold water stranding bath, chopped and recovered.

Example 23

The homopolymer polypropylene was fed to Barrel 1 of an 11 barrelCentury™ brand co-rotating twin screw extruder using a standard K-Tronloss-in-weight pellet feeder system. Molten maleic anhydride was pumpedthrough a spring loaded injector into Barrel 3, port 1, at 130° F. usinga high pressure pump and heated lines. Lupersol 101 peroxide was pumpedthrough a spring loaded injector into Barrel 6, port 1 using a highpressure injection pump. Barrel 1 was set at a temperature of 200° F.,and Barrels 2 through 11 were set at 400° F. The extruder rpm wasincreased to 180 and held constant for the duration of the experiment.After the extruder barrels were at the designated temperature, thefeeders were turned on and the extruder was started up using methodsknown to those skilled in the extruder art of slowly increasing the rpmand feeds to target levels to prevent high torque shutdown of theextruder. Target rates for the feeds were as described above.

The extruder screw profile was set up using standard screw elementsarranged to convey the homopolymer polypropylene feed forward from thefeed port at Barrel 1 and force it through a set of kneading blocksdesigned to melt the polypropylene in a first melting zone. After thepolypropylene was melted, the molten maleic anhydride was then injectedinto the already molten polypropylene and the two materials were mixedin a first mixing zone to form a blend. This first mixing zone waslocated down stream from the first melting zone of the extruder and wascomprised of distributive mixing elements followed by melt sealingelements. The peroxide initiator, Lupersol 101, was injected into theextruder and mixed with molten blend of polypropylene and maleicanhydride in a second mixing zone to form a reaction mixture. Thissecond mixing zone was comprised of distributive mixing elementsfollowed by melt sealing elements for mixing the reaction mixture for asufficient time to produce the desired maleic grafted polypropylene.

The amount of time the reaction mixture remains in the extruder is afunction of the feed rates of the reactants, extruder size, screw designand rpm of operation can be optimized by those skilled in the art usingroutine experimentation. While in the extruder, the reaction mixture wassubjected to a vacuum to remove volatile materials, followed by recoveryof the maleic grafted polypropylene using a standard strand bath andstrand pelletizer. The cylindrical shaped pellets were captured afterscreening to separate both longs and fines using a standard vibratingscreener.

The grafted polypropylene had an acid number=8, a Brookfieldviscosity=79,000 centipoise, a Yellowness Index=36.5, and number averagemolecular weight Mn=29,561.

Example 24

In Example 24, the method of making the grafted polypropylene inaccordance with the present invention was generally the same as Example23 except for the following changes: the molten maleic feed rate wasincreased from 25 to 26.5 pounds/hour and the peroxide feed rate wasreduced from 4.68 to 4.3 pounds/hour.

The grafted polypropylene had an acid number=7.6, a Brookfieldviscosity=180,000 centipoise, a Yellowness Index=41.9, and numberaverage molecular weight Mn=32,230.

Having described the invention in detail, those skilled in the art willappreciate that modifications may be made to the various aspects of theinvention without departing from the scope and spirit of the inventiondisclosed and described herein. It is, therefore, not intended that thescope of the invention be limited to the specific embodimentsillustrated and described but rather it is intended that the scope ofthe present invention be determined by the appended claims and theirequivalents. Moreover, all patents, patent applications, publications,and literature references presented herein are incorporated by referencein their entirety for any disclosure pertinent to the practice of thisinvention.

1. A composition of matter comprising a maleated polypropylene having anacid number greater than 6, a yellowness index color of no greater than76, and a number average molecular weight of at least 20,000.
 2. Thecomposition according to claim 1 wherein said acid number is between 9and
 60. 3. The composition according to claim 1 wherein said yellownessindex color is less than
 60. 4. The composition according to claim 1wherein said yellowness index color is less than
 40. 5. The compositionaccording to claim 1 wherein said number average molecular weight isbetween 20,000 and 100,000.
 6. The composition according to claim 1wherein said maleated polypropylene contains less than 20 weight percentcomonomer.
 7. The composition according to claim 1 wherein said maleatedpolypropylene contains less than 5 weight percent comonomer.
 8. Thecomposition according to claim 6 wherein said maleated polypropylene isa homopolymer of propylene.
 9. A maleated polypropylene having an acidnumber greater than 6, a yellowness index color of no greater than 76,and a number average molecular weight of at least 20,000 prepared by theprocess comprising: a. in a reactor, forming a molten mixture comprisinga polypropylene and maleic anhydride; b. mixing a reaction initiatorinto the molten mixture under condition suitable for producing a producthaving said maleic anhydride grafted onto said polypropylene; and c.recovering said product, wherein the weight ratio of polypropylene tomaleic anhydride is about 10 to 200, the molar ratio of polypropylene tofree radical initiator is about 200 to 4,000, and the molar ratio ofmaleic anhydride to free radical initiator is about 1 to
 70. 10. Themaleated polypropylene of claim 9 wherein said process further comprisessubjecting the product to a vacuum to remove volatiles.
 11. The acidgrafted polypropylene of claim 9 wherein said maleated polypropylene hasan acid number greater than 6, a yellowness index color no greater than56, a number average molecular weight of at least 20,000, and aBrookfield viscosity of at least 79,000 cP.
 12. The acid graftedpolypropylene of claim 9 wherein said maleated polypropylene has an acidnumber greater than 7.6, a yellowness index color no greater than 50, anumber average molecular weight of at least 20,000, and a Brookfieldviscosity of at least 79,000 cP.
 13. The acid grafted polypropylene ofclaim 9 wherein said yellowness index color is less than
 40. 14. Theacid grafted polypropylene of claim 9 wherein the weight ratio ofpolypropylene to maleic anhydride is about 25 to
 60. 15. The acidgrafted polypropylene of claim 9 wherein the molar ratio of maleicanhydride to free radical initiator is about 9.5 to about
 108. 16. Theacid grafted polypropylene of claim 15 wherein said grafting step isconducted at a temperature of from between 190 and 205° C.
 17. The acidgrafted polypropylene of claim 9 wherein said reactor for grafting saidmaleic anhydride onto said polypropylene is a twin screw extruder. 18.The acid grafted polypropylene of claim 9 wherein said reactioninitiator is a peroxide selected from the group consisting of ditertiarybutyl peroxide, tertiary butyl hydroperoxide, cumene hydroperoxide,p-menthane peroxide, p-menthane hydroperoxide and2,5-dimethyl-2,5-bis-(t-butylperoxy) hexane.